1. Field of the Invention
The present invention relates to an light emitting diode (LED) element used for display apparatus, indication lamp or similar applications, and particularly to an LED element that makes it possible to reduce man-hours required in the operation of mounting the LED element on a circuit board and allows high-density packaging on the circuit board.
2. Background Art
An example of a method for manufacturing an LED element 90 of the prior art is shown in FIGS. 1 and 2. First, as shown in FIG. 1, an N layer 91b of GaAsP and then an N+ layer 91c of GaAsP are formed on one side of a heavily-doped N type base layer 91a of GaP by diffusion or other proper means, thereby to obtain an LED substrate 91. Insulation films 92, 93 made of SiO.sub.2 or the like are formed on the front and back sides of the LED substrate 91, respectively. Provided in the insulation film 92 on the front side are apertures 92a at portions that will be subjected to a subsequent diffusion process.
The LED substrate 91 and a P-type diffusing substance 94 (for example Zn) are put into a quartz tube 81 under vacuum condition, as shown in FIG. 2, and subjected to heat treatment at a temperature from 700 to 800.degree. C. This causes the P-type diffusing substance 94 to be diffused over the apertures 92a, thereby forming PN junctions 95 (refer to FIG. 3).
After the process described above, the LED substrate 91 is taken out of the quartz tube 81 and undergoes such processes as removal of unnecessary portions of the insulation film 93, formation of a P electrode 96 and an N electrode 97 and cut-off. Thus the LED element 90 as shown in FIG. 3 is obtained. The LED element 90 thus obtained is mounted on a circuit board, a lead frame or the like to suit the application, fitted with wiring to the P electrode 96 using gold wire or the like and is provided with a case, thereby to make a product such as an LED display or LED lamp.
In the LED element 90 of the prior art described above, however, the P electrode 96 and the N electrode 97 are formed on different sides, the former on the front side and the latter on the back side, of the LED element 90. Consequently, wiring for the electrodes 96 and 97 must be done separately in different processes. Thus the manufacturing processes for the LED element of this configuration becomes complicated.
Particularly the P electrode 96, because of the location thereof being on the top surface of the LED element 90 when mounted, requires three-dimensional wiring that involves wires running over other components. This makes it necessary to provide a certain clearance around the LED element 90, making it impossible to mount the LED elements 90 with a high density. As a result, there occurs such a problem that display quality cannot be improved due to the packaging density when a display apparatus is formed.